Removal of a significant volume of tissue, as is frequently necessary in cancer surgery, confronts the surgeon with special technical and physiological problems. Removal of a significant volume of tissue often makes it difficult to close the wound properly, and when closing is achieved, the tissue scars and the stitches restrict the mobility, which disabilitates the patient. The enclosed wounds can collapse or fill with fluids and cell poor scar tissues. The results are often disabling scar tissue formation, infections, pain, cosmetic anomalies or even complete loss of function of the effected body parts. For example, after surgical removal of a breast tumour, the contraction of the wound cavity often leads to shrinkage of the breast that by far exceeds the volume of the originally removed tissue. Furthermore, adjuvant radiation therapy increases the above mentioned problems drastically. Today, these post-surgical conditions are treated by silicon inlays, secondary palliative surgery, pain and infection controlling drugs, or in the worst case by amputation. Needles to say, these conditions and measurements all cause severe problems for the patients, physically, esthetical and emotionally.
Enamel matrix proteins, present in the enamel matrix, are most well-known as precursors to enamel. Prior to cementum formation, enamel matrix proteins are deposited on the root surface at the apical end of the developing tooth-root. There is evidence that the deposited enamel matrix is the initiating factor for the formation of cementum. Again, the formation of cementum in itself is associated with the development of the periodontal ligament and the alveolar bone. As shown by the present inventors prior to the present invention, enamel matrix proteins can therefore promote periodontal regeneration through mimicking the natural attachment development in the tooth (Gestrelius S, Lyngstadaas SP, Hammarstrøm L. Emdogain—periodontal regeneration based on biomimicry. Clin Oral Invest 4:120–125 (2000).
The enamel matrix is composed of a number of proteins, such as amelogenin, enamelin, tuft protein, proteases, and albumin. Amelogenins, the major constituent of the enamel matrix, are a family of hydrophobic proteins derived from a single gene by alternative splicing and controlled post secretory processing. They are highly conserved throughout vertebrate evolution and demonstrate a high overall level of sequence homology among all higher vertebrates examined (>80%). In fact, the sequences of porcine and human amelogenin gene transcript differ only in 4% of the bases. Thus, enamel matrix proteins, although of porcine origin, are considered “self” when encountered in the human body and can promote dental regeneration in humans without triggering allergic responses or other undesirable reactions.
Enamel matrix derivative (EMD), in the form of a purified acid extract of proteins from pig enamel matrix has previously been successfully employed to restore functional periodontal ligament, cementum and alveolar bone in patients with severe tooth attachment loss (Hammarström et al., 1997, Journal of Clinical Periodontology 24, 658–668).
In studies on cultured periodontal ligament cells (PDL), it was furthermore shown that the attachment rate, growth and metabolism of these cells were significantly increased when EMD was present in the cultures. Also, cells exposed to EMD showed increased intracellular cAMP signalling and autocrine production of growth factors, when compared to controls. Epithelial cells on the other hand, increased cAMP signalling and growth factor secretion when EMD was present, but their proliferation and growth were inhibited (Lyngstadaas et al., 2001, Journal of Clinical Periodontology 28, 181–188).
Enamel proteins and enamel matrix derivatives have previously been described in the patent literature to be able to induce hard tissue formation (i.e. enamel formation, U.S. Pat. No. 4,672,032 (Slavkin)), binding between hard tissues (EP-B-0 337 967 and EP-B0 263 086) and open wound healing, such as of skin and mucosa (WO 9943344).
The present application relates to the beneficial effects of EMD on guided connective soft tissue growth and resistance to contraction in closed wounds following loss or removal of significant volumes of tissue, such as e.g. after tumour surgery and especially in combination with radiation therapy, effects that are both unexpected and surprising.